Warhead and method of making same

ABSTRACT

A warhead and the method of making same by cutting a tube blank from a length of metal tubing at a position on the length of tubing which will result in the blank containing the amount of material required in the finished warhead, cold extruding the blank to elongate the blank and to form an enlarged annular section about a first end, cold extruding the blank to taper the blank toward the second end, cold extruding the blank to move the enlarged section radially inward so that the blank has a substantially constant diameter form the first end to the taper, and cold extruding the blank to taper the first end. During or before the first or an early extrusion step groove may be formed in the surface of the blank so that during a subsequent extruding step metal adjacent the grooves if forced and moved together to smooth the surface and establish fault lines so as to control the fragmentation pattern of the warhead.

United States Patent [72] inventor Robert Lovell Bloomfield Hills, Mich.[2]] Appl. No. 778.249 [22] Filed Nov. 22, I968 [45] Patented July 27,1971 I73] Assignee Lawrence B. Boenscli Birmingham, Mkli.

a part interest {54] WARHEAD AND METHOD OF MAKING SAME 26 Claims, 7Drawing Figs.

[52] US. Cl. 2911.2, l02l92.5 [S1] Int.Cl ..B2lk21l06 [$0] FleldofSenrch ..29/l.2, L2]

[56] References Cited UNITED STATES PATENTS l,l3l,973 3/l9l5 While29/].2 2,325,079 7/1943 Soderholm 20H .2 X 2,663,068 l2/l953Towner....................,... 29/12 3,0l9,733 2/[962 Braid 29/l.2X

Primary Examiner-Harrison L. Hinson AnorneyBarnard, McGlynn & ReisingABSTRACT: A warhead and the method of making same by cutting a tubeblank from a length of metal tubing at a position on the length oftubing which will result in the blank containing the amount of materialrequired in the finished warhead, cold extruding the blank to elongatethe blank and to form an enlarged annular section about a first end,cold extruding the blank to taper the blank toward the second end, coldextruding the blank to move the enlarged section radially inward so thatthe blank has a substantially constant diameter form the first end tothe taper, and cold extruding the blank to taper the first end. Duringor before the first or an early extrusion step groove may be formed inthe surface of the blank so that during a subsequent extruding stepmetal adjacent the grooves if forced and moved together to smooth thesurface and establish fault lines so as to control the fragmentationpattern of the warhead.

maminm sum 1 BF 2 WAIIIIEAD AND METHOD OF MAKING SAME This inventionrelates to a warhead and the method of making the same. The inventionhas been found very satisfactory for warheads of the type utilircd inmortars. This type of warhead is sent through the air in a trajectory tothe target. The weight of the warheads must, therefore, be maintainedwithin very close tolerances otherwise the trajectory and the closenessof the hit to the target can be seriously affected. Additionally, thewarhead must have an outer surface which is aerodynamically andballistically stable. Furthermore, such a warhead is an antipersonnelexplosive device and should fragment into many small pieces upondetonation.

An example of a warhead of this type is one approximately l inches longand a little over 3 inches in diameter at the largest portion and havinga wall thickness of approximately onequarter inch.

warheads of this type have heretofore and are now being made by castingor hot extrusion.

A warhead made by casting inherently has a high degree of porosity andmust be machined on all surfaces including both the complete inner andouter diameters of the warhead. The warhead must be machined to theproper weight and in the case of castings the reduction in weight due tothis machining approximates 50 percent. The warhead is also machined toin sure against porosity and to smooth the outer surface for aerodynamicstability. All warheads must pass hydrostatic and air pressure tests, asfor example, hydrostatically being subjected to 6,000 p/.s.i. for 6seconds. Because of the high porosity in castings, even after machining,the scrap rate of warheads made by casting is extremely high, i.e., avery high percentage of such warheads fail the hydrostatic test.Warheads made by casting are, relative to the instant invention, veryexpensive due to the precise machining necessary and the attendant lossof material thereby and because of the high scrap rate for failure topass the air and hydrostatic test.

In making the warheads by hot extrusion, a heated oversized billet ispressed into a cup-shape and then extruded. This process also requiresextreme metal removal by machining.

In warheads made by either casting or hot extrusion it is verydifficult, and frequently impossible to provide a fragmentation patternwhich is consistent.

Accordingly, it is an object and feature of this invention to provide animproved warhead and the method for making same which results in ahigher quality warhead at a significantly reduces cost.

Another object and feature of this invention is to provide a method ofmaking a warhead wherein; the material loss is insignificant, whichrequires negligible machining, and wherein the tolerances from warheadto warhead are very consistent.

Another object and feature of this invention is to provide a warhead andthe method of making same wherein the fragmentation pattern issubstantially consistent.

Another object and feature of this invention is to provide a method ofmaking a warhead by cold extruding a metal tubular blank so as toelongate the blank and form a precise enlarged annular section about oneend thereof and thereafter extruding the blank to move the enlargedannular section radially inwardly to develop the precise amount ofmaterial and dimensions in the ogive section of the warhead andthereafter tapering and/or nosing the ends of the blank.

In correlation with the foregoing objects and features, another objectand feature of this invention is to provide a warhead having the desiredfragmentation pattern by forming grooves in the warhead prior to one ofthe cold extruding steps so that during a subsequent cold extruding stepmetal adjacent the grooves is forced together to smooth the surface andform fault lines.

Other objects and attendant advantages of the present in vention will bereadily appreciated as the same becomes better understood by referenceto be following detailed description when considered in connection withthe accompanying drawings wherein:

FIG. I is a view of a length of pipe from which tubular blanks are cut',

FIG. 2 discloses the extruded tubular blank as extruded to be elongatedand to have an enlarged annular section about one end;

FIG. 3 shows the tubular blank with the second end thereof beingtapered;

FIG. 4 discloses the tubular blank with the enlarged annular section atthe first end thereof having been moved radially inwardly;

FIG. 5 discloses the blank with the first end thereof having beentapered;

FIG. 6 is a cross-sectional view taken substantially along line 6-6 ofFIG. 2; and

FIG. 7 is an enlarged view of the tubular blank with grooves in theouter surface thereof prior to the first extruding step.

FIG. I discloses a length of tube I0. Initially, a tubular blank 12 iscut from the length of tube at a position 14 on the length of tube whichwill result in the blank 12 containing the amount of material requiredin the finished warhead. The length of tube It] utilized in the instantmethod is preferably of a high quality in that it has a consistentdensity along its entire length. After the first blank 12 has been cutfrom the length of tubing I0, it is weighed to make sure that it is ofthe proper weight. If the first blank is not at the proper weight, theposition I4 is adjusted accordingly so that the next blank does have theexact weight and amount of material required for the final or finishedwarhead. Instead of weighing the blank, the length of the blank may bechanged if after one or more extruding steps, the volume in the blank isfound to be out of tolerance. It has been found satisfactory to usemedium or low-carbon steels as well as alloy steels such as SAE I0l 8 orSAE I340 steel.

As will be understood to those skilled in the art, the steps describedand illustrated hereinafter may be performed simultaneously with othersteps and in varying sequences.

As illustrated in FIG. 2, an initial step is to cold extrude the metaltubular blank to elongate it and to simultaneously form an enlargedannular section 16 about a first end thereof. In this step the blank iscold worked to reduce the wall thickness or the cross-sectional area ofthe material. This is accomplished by forcing the blank through a firstfemale die 18 with the punch 20 and the sleeve 22, the sleeve 22engaging the upper end of the blank I2. The female die 18 has a land 24through which the blank is forced so as to be elongated as the wallthickness thereof is reduced. As shown at 25, there is a relief belowthe land 24, i.e., the die 18 has a larger diameter below the land 24than the diameter of the land itself. A radius of between 0.40 and 0.70inches leading into the land 24 has been satisfactory, although this mayvary with changes in other parameters. In an example, the blank I2 isapproximately 6-3/4 inches long and is elongated to approximately 9inches long during the step illustrated in FIG. 2. In FIG. 2, as in theremaining FIGS. the large metal member shown in cross section andsurrounding the extruding members are support and retaining members ofthe type well known in the art.

The next step illustrated is that of FIG. 3 wherein the blank isextruded to taper the second end thereof as indicated at 26. This isaccomplished by forcing the blank into the tapered female die 28 with atapered punch 30 and sleeve 32. It will be noted that the tapered femaledie 28 has a shoulder 34 for engaging the enlarged angular section atthe first end of the blank.

The fourth step is illustrated in FIG. 4, wherein the blank is extrudedto move the enlarged section 16 radially inwardly so that the outerdiameter of the blank is substantially constant from the first endthereof to the taper 26. This is accomplished by forcing the blankdownwardly through the die member 36 which has the land 38 for forcingthe enlarged angular section l6 radially inwardly. Again, there is arelief 39 below the land 38. The upper end of the blank is engaged bythe punch 40.

The last step is illustrated in FIG. 5 wherein the first end of theblank is nosed by the female die 42 as the blank is held in position bythe tapered member 44.

Each of the steps subsequent to the step illustrated in FIG. 2 is also acold extruding step in that the blank changes shape and size ordimension and in one example is actually elongated approximately onehundred and fifty to three hundred thousandths of an inch in each step.Also, as will be specified hereinafter, the physical characteristics andthe mechanical properties of the blank are altered during each step.

Preferably grooves are formed in the surface of the blank prior to oneof the extruding steps so that a subsequent extruding step forces themetal adjacent the grooves together to smooth the surface andmechanically establish fault lines. Such grooves are preferably formedin the blank 12 before the first cold extruding step, as illustrated inFIG. 7 but at least some of the grooves may be formed either on theinner or outer diameter during the first cold extruding step, formingthe grooves on the inner diameter by extruding is illustrated in FIG. 2.

A blank 12 is illustrated in FIG. 7 with longitudinal grooves 52 andcircumferential grooves 54. These grooves are formed prior to the firstcold extrusion step illustrated in FIG. 2 The grooves 54 are formed inthe surface of the blank transversely to the first mentionedlongitudinal grooves 52. The grooves 54 are disposed circumferentiallyabout the blank and are defined by a single-helical groove. The grooves52 and 54 are preferably formed by moving metal as by cold rollingalthough may be formed by cutting the blank to remove materialtherefrom. Cutting, however, must be done very accurately to control thefinal weight of the warhead. Once the grooves 52 and 54 are formed inthe warhead blank the metal adjacent the groove: is forced togetherduring the first extruding step thereby smoothing the surface andestablishing the mechanical fault lines. A fault line is the interfacewhere the metal adjacent the grooves is forced together so as to becontiguous and nonhomogeneous at the interface yet whereby the outersurface is smooth and such lines are substantially invisible to thenaked eye. These fault lines may be on the inner or outer surface of thewarhead but are preferably on the outer surface of the warhead becauseupon detonation die warhead balloons which tends to separate the metalalong the fault lines so that the warhead will fragmentize along thefault lines into numerous identical fragments.

As alluded to'above, the grooves may also be formed on the outside orinside of the blank by cold extruding. An example of extruding thegrooves on the inner diameter is shown in FIG. 2 wherein the punch issplined so as to have spaced ridges 50 which form grooves on the innersurface of the blank during the first extruding step. Thecircumferential curves may be then formed on either the inner or outersurface after the first extruding step by cold rolling or threading. Thesubsequent extruding steps smooth the surface to establish the faultlines.

The finished warhead, therefore, has a very smooth outer surface and iswithin strict tolerances as to its weight. One last step is performed onthe warhead in the configuration illustrated in FIG. 5 and that is toform threads along the surface for receiving a detonation device. Theforming of these threads can be accurately controlled so as to provide awarhead having a weight within specified tolerances.

When using a steel having a tensile of approximately 96,000 p.s.i., ahardness of approximately 92 as measured on the Rockwell B Scale, ayield strength of approximately 75,000 p.s.i., and the elongation beingapproximately 23 percent, the mechanical properties of the blank arealtered during the extrusion steps described so that the finishedwarhead has a hardness of approximately 31 on the Rockwell C Scale, atensile of approximately 145,000 p.s.i., a yield strength ofapproximately 140,000 p.s.i., and the elongation being approximately 10percent which, of course, perfects the fragmentation of the warhead upondetonation. It is also to be noted that low-car bon steel could not besatisfactorily utilized in the prior methods for making warheads becausethe finished warhead would fragmentize into large pieces. However,low-carbon steel can be utilized with the instant method including thegrooving thereof because such establishes a fragmentation pattern suchthat the warhead of low-carbon steel fragmentizes into a large number ofsmall pieces.

In forming a warhead by casting or hot forging as described hereinabove,the wall thickness can be maintained within a tolerance of plus or minusthirty thousandths whereas the wall thickness of the warhead made inaccordance with the instant method may be maintained between 5 and i0thousandths. Furthermore, the dies utilized to cold extrude the warheadin accordance with the instant invention may be revised in size veryeasily to change the desired weight of the finished warhead.Additionally, a warhead may be made in accordance with the instantinvention at a cost which is approximately one-third less than the costof a warhead made by casting or hot forging. Although the step ofreducing the diameter of the first end of the warhead has been referredto as nosing because, as illustrated. it does not have a straight taperwhereas the second does, it will be understood that in the general sensethese terms are interchangeable.

The invention has been described in an illustrative manner and it is tobe understood that the terminology which has been used is intended to bein the nature of words of description rather than of limitation.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

I. A method of making a warhead comprising the steps of: cold extrudinga metal tubular blank to form an enlarged annular section about a firstend thereof, and cold extruding the blank to move the enlarged sectionradially inward.

2. A method as set forth in claim 1 further defined as cold extrudingthe blank to elongate the blank while forming said enlarged section.

3. A method as set forth in claim 2 further defined as cold extrudingthe blank to nose the first end and to taper the second end thereof.

4. A method as set forth in claim 3 further defined as first coldextruding the blank to taper the second end thereof and then coldextruding the blank to move the enlarged section radially inward so thatthe blank has a substantially constant diameter from the first endthereof to the taper end then cold extruding the blank to nose the firstend thereof.

5. A method as set forth in claim 4 including initially cutting thetubular blank from a length of tubing at a position on the length oftubing which will result in the blank containing the amount of materialrequired in the finished warhead.

6. A method as set forth in claim 4 wherein said blank comprises steelhaving a tensile of approximately 96,000 p.s.i., a hardness ofapproximately 92 I IS measured on the Rockwell B Scale, I yleld strengthof approxlmately 75,000 p.s.i. and the elongation being approximately 23percent.

7. A method as set forth in claim 4 wherein said blank comprises one ofSAE 1018 and SAE 1340 steel.

8. A method as set forth in claim 5 including forming grooves in thesurface of said blank prior to one of said extruding steps so that asubsequent extruding step forces the metal together to smooth thesurface and establish fault lines.

9. A method as set forth in claim 8 further defined as forming saidgrooves in said blank prior to the first cold extruding step.

10. A method as set forth in claim 8 further defined as forming thegrooves in one of the inner and outer surfaces of said blank andincluding the step of forming other grooves in one of said surfacestransverse to said first mentioned grooves.

II. A method as set forth in claim 10 further defined as forming saidother grooves prior to one of said extruding steps so that a subsequentextruding step forces the metal together and smooths the surface toestablish fault lines.

[2. A method as set forth in claim further defined as forming said firstmentioned grooves longitudinally along said blank.

13. A method as set forth in claim 12 further defined as forming saidother grooves circumfcrentially about said blank.

14. A method as set forth in claim 13 further defined as forming saidfirst mentioned grooves by extruding said blank with a member havingridges.

15. A method as set forth in claim 14 further defined as forming saidother grooves by forming a helical groove.

[6. A method as set forth in claim 15 further defined as moving metal toform said helical groove.

l7. A method as set forth in claim l6 further defined as forming all ofsaid grooves in the outer surface of said blank.

18. A method of making a warhead which will fragmentize in apredetermined pattern comprising the steps of; forming grooves in asurface ofa warhead blank, and forcing the metal adjacent the groovestogether to smooth said surface and establish fault lines.

19. A method as set forth in claim l8 further defined as cold extrudingsaid blank to smooth said surface and establish fault fill lines.

20. A method as set forth in claim 18 further defined as forming saidgrooves by cold extruding.

21. A method as set forth in claim 20 wherein said blank is a generallytubular member and further defined as forming said grooveslongitudinally along the surface of said blank.

22. A method as set forth in claim 2] further defined as forming saidgrooves by extruding said blank with a member having ridges thereabout.

23. A method as set forth in claim 20 including the step of formingother grooves in a surface of said blank transverse to said firstmentioned grooves.

24. A method as set forth in claim 23 further defined as extruding saidblank to force the metal adjacent said other grooves together to smoothsaid surface and establish fault lines.

25. A method as set forth in claim 24 wherein said other grooves areformed by a helical groove.

26. A method as set forth in claim 25 further defined as moving metal toform said helical groove.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3,594,88Dated July 227 1971 Inventor(s) Robert Lovell It is certified that errorappears in the above-identified patent t and that said Letters Patentare hereby corrected as shown below:

Abstract, line 9 "form" should be --from--; abstract, line 12 "groove"should be --grooves--. Column 1, line #7 "reduces" should be--reduoed--; column 1, line 73 "he" should be --the--. Column 4, line 3of Claim 6 after 92 delete "l".

Signed and sealed this 26th day of March 1 972.

(SEAL) Attest:

EDWARD M.FLETCHER, JR. ROBERT GOTTSCHALK Attesting OfficerCommissionerof Patents FORM PO-1050 (10-69) USCOMM-DC 60376-P69 9 U S,GOVERNMENY PRINTING OFFICE I569 O365-334

1. A method of making a warhead comprising the steps of: cold extrudinga metal tubular blank to form an enlarged annular section about a firstend thereof, and cold extRuding the blank to move the enlarged sectionradially inward.
 2. A method as set forth in claim 1 further defined ascold extruding the blank to elongate the blank while forming saidenlarged section.
 3. A method as set forth in claim 2 further defined ascold extruding the blank to nose the first end and to taper the secondend thereof.
 4. A method as set forth in claim 3 further defined asfirst cold extruding the blank to taper the second end thereof and thencold extruding the blank to move the enlarged section radially inward sothat the blank has a substantially constant diameter from the first endthereof to the taper end then cold extruding the blank to nose the firstend thereof.
 5. A method as set forth in claim 4 including initiallycutting the tubular blank from a length of tubing at a position on thelength of tubing which will result in the blank containing the amount ofmaterial required in the finished warhead.
 6. A method as set forth inclaim 4 wherein said blank comprises steel having a tensile ofapproximately 96,000 p.s.i., a hardness of approximately 92 l asmeasured on the Rockwell B Scale, a yield strength of approximately75,000 p.s.i. and the elongation being approximately 23 percent.
 7. Amethod as set forth in claim 4 wherein said blank comprises one of SAE1018 and SAE 1340 steel.
 8. A method as set forth in claim 5 includingforming grooves in the surface of said blank prior to one of saidextruding steps so that a subsequent extruding step forces the metaltogether to smooth the surface and establish fault lines.
 9. A method asset forth in claim 8 further defined as forming said grooves in saidblank prior to the first cold extruding step.
 10. A method as set forthin claim 8 further defined as forming the grooves in one of the innerand outer surfaces of said blank and including the step of forming othergrooves in one of said surfaces transverse to said first mentionedgrooves.
 11. A method as set forth in claim 10 further defined asforming said other grooves prior to one of said extruding steps so thata subsequent extruding step forces the metal together and smooths thesurface to establish fault lines.
 12. A method as set forth in claim 10further defined as forming said first mentioned grooves longitudinallyalong said blank.
 13. A method as set forth in claim 12 further definedas forming said other grooves circumferentially about said blank.
 14. Amethod as set forth in claim 13 further defined as forming said firstmentioned grooves by extruding said blank with a member having ridges.15. A method as set forth in claim 14 further defined as forming saidother grooves by forming a helical groove.
 16. A method as set forth inclaim 15 further defined as moving metal to form said helical groove.17. A method as set forth in claim 16 further defined as forming all ofsaid grooves in the outer surface of said blank.
 18. A method of makinga warhead which will fragmentize in a predetermined pattern comprisingthe steps of; forming grooves in a surface of a warhead blank, andforcing the metal adjacent the grooves together to smooth said surfaceand establish fault lines.
 19. A method as set forth in claim 18 furtherdefined as cold extruding said blank to smooth said surface andestablish fault lines.
 20. A method as set forth in claim 18 furtherdefined as forming said grooves by cold extruding.
 21. A method as setforth in claim 20 wherein said blank is a generally tubular member andfurther defined as forming said grooves longitudinally along the surfaceof said blank.
 22. A method as set forth in claim 21 further defined asforming said grooves by extruding said blank with a member having ridgesthereabout.
 23. A method as set forth in claim 20 including the step offorming other grooves in a surface of said blank transverse to saidfirst mentioned grooves.
 24. A method as set forth in claim 23 furtherdefined as extruding said blank to force the metal adjacent said othergrooves together to smooth said surface and establish fault lines.
 25. Amethod as set forth in claim 24 wherein said other grooves are formed bya helical groove.
 26. A method as set forth in claim 25 further definedas moving metal to form said helical groove.